The present invention relates to a method for machining molded or an elastomeric coated part, and a machine tool for performing the machining.
Valves having an elastomeric or elastomeric-coated valve component are commonly used to ensure a tight seal between the valve and an associated structure when the valve is closed. The valve component is typically connected to a valve stem for positioning the valve component in an open or closed position. For example, a wedge gate valve is commonly used to control the flow of fluid through a pipe or conduit, particularly in waterworks and gas services. As illustrated, the conventional wedge-shaped disk has a T-shaped slot or cavity formed in an upper portion for receiving a corresponding T-shaped free end or T-nut of the valve stem member for connecting the disk to the stem member.
Molding, such as injection molding, is a common process of making elastomeric or elastomeric parts, such as coated valve components. For example, with injection molding, melted resin (i.e., elastomeric material) is injected at a high pressure into a cavity of a mold. The resin solidifies in the mold to form the valve component. The mold comprises at least two parts, each part defining a portion of the cavity of the mold. The mold is adapted to be separated after the molding process to allow for the molded valve member to be extracted from the mold. During the molding process, excess resin called “flash” flows beyond the edges of the mold into the location where the parts of the mold come together (called the “parting line”). The flash freezes to form a thin, sheet-like protrusion from the valve component.
It is desirable to trim the flash, particularly flash present in a slot of an applicable valve because the slot is sized and shaped to snugly receive the valve stem and the presence of flash or at least access flash inside the slot may interfere with or even prevent the ability of the valve stem to fit in the slot. The flash is conventionally trimmed manually using either a hot or cold cutting device such as a razor or a knife. This process, however, is inefficient, labor-intensive and time-consuming because the trimming is performed manually. Moreover, the quality of manually trimmed slots may be poor. For example, a worker may fail to trim an adequate amount of the flash, making it difficult to fit the valve stem in the slot, or the worker may trim beyond the flash, into the elastomeric coating, creating gaps between the valve stem and the slot when the stem is received in the slot.